First off, I like the quilt and you did a fabulous job matching the points. The sample block you did with the arches suggests you are in good control of the quilt and could maybe follow a drawn pattern.
Since the quilt has a lot of white, white should be used as the color of the batting. Laying it over any other color will show the seam allowances.
Since the "sashing" is fairly narrow, I'd stitch in the ditch. Now for the large blocks. The white reads as large blocks and could have a pattern inside them. There are lots of block patterns in books. Mark the white before making the sandwich. The arches woud look good for the smaller colored squares.
Having said all this, my favorite is FMQ.
It's advise, but it's your quilt.